The French patent publication No. 2,130,629 discloses a method wherein triglycine sulfate is utilized as a ferroelectric or pyroelectric material. The triglycine sulfate, in the form of a fine suspension in a liquid in which it is not soluble, is deposited on the top surface of the substrate by a simultaneous application of an electric field.
Further, measurements made on large sodium nitrite crystals (F. Jona, G. Shirane, Ferroelectric Crystals, Pergamon Press 1962), indicate that sodium nitrite is a ferroelectric material. However, sodium nitrite has, up to now, not been taken into consideration for the manufacture of solid ferroelectric or pyroelectric building blocks, because no advantages relative to the known ferroelectric materials such as barium titanate and triglycine sulfate were recognized.